The present invention relates, in general, to a gradual release mechanism for a railway car hand brake and, more particularly, this invention relates to a hand brake operating shaft assembly with a reduced release torque.
Prior to the present invention, when controlled release of a hand brake for a railway car is desired, a hand wheel is moved in a counterclockwise direction. This movement has the effect of turning a threaded operating shaft relative to a threaded sleeve so as to sufficiently free the clutch flange surfaces on the operating shaft and the sleeve from the mating surfaces of the ratchet wheel.
When the counterclockwise movement of the hand wheel ceases, the tension on the brake chain allows the sleeve to return to full clamping relation with the ratchet wheel.
The torque required for overcoming the clamping forces created as a result of friction between the mating threaded surfaces of the operating shaft and the sleeve, and the clutch flange surfaces on the ratchet wheel to release the hand brake is typically at or above the input torque.
An example of this type hand brake is taught in U.S. Pat. No. 3,923,287. The teachings of this reference are incorporated herein by reference thereto.
There are several disadvantages to this current design. For example, the continuous high forces necessary to overcome the frictional forces of the present design will result in premature wear and subsequent replacement of parts. Finally, the potential for failure may exist in service if prematurely worn parts are not detected and replaced in a timely manner.
In a first aspect, the present invention provides a gradual release mechanism for a hand brake. The mechanism includes an operating shaft for rotation about an axis extending longitudinally of the shaft. A clutch flange portion is disposed intermediate both ends of the operating shaft, with the clutch flange having a clutch surface. A sleeve is concentrically disposed and threadedly mounted on the operating shaft for rotational movement. The sleeve comprises a clutch collar having a clutch surface opposed to the clutch surface of the operating shaft clutch flange portion. An externally threaded surface on the operating shaft is engageable with an internally threaded surface on the sleeve, having a pitch between about 0.60 inch and about 1.00 inch. A ratchet wheel is received about the operating shaft, having oppositely disposed clutch surfaces positioned for engagement by the clutch collar portions of the operating shaft and the sleeve. A pinion is journaled on the operating shaft and is adjacent to the sleeve.
In a further aspect, the present invention provides a gradual release mechanism for a hand brake. The mechanism includes an operating shaft for rotation about an axis extending longitudinally of the shaft. A clutch flange portion is disposed intermediate both ends of the operating shaft, with such clutch flange having a clutch surface. A sleeve is concentrically disposed and threadedly mounted on the operating shaft for rotational movement. The sleeve comprises a clutch collar having a clutch surface opposed to the clutch surface of such operating shaft clutch flange portion. An externally threaded surface on the operating shaft is engageable with an internally threaded surface on the sleeve. A ratchet wheel is received about the operating shaft, having oppositely disposed clutch surfaces positioned for engagement by the clutch collar portions of the operating shaft and the sleeve. A pinion is journaled on the operating shaft and is adjacent to the sleeve. At least one friction plate is engageable at least one of the clutch surfaces of the clutch flange and the clutch collar, respectively, and a clutch surface of the ratchet wheel.
In still a further aspect, the present invention provides a gradual release mechanism for a hand brake. The mechanism includes an operating shaft for rotation about an axis extending longitudinally of the shaft. A clutch flange portion is disposed intermediate both ends of the operating shaft, with clutch flange having a clutch surface. A sleeve is concentrically disposed and threadedly mounted on the operating shaft for rotational movement. The sleeve comprises a clutch collar having a clutch surface opposed to the clutch surface of operating shaft clutch flange portion. An externally threaded surface on the operating shaft is engageable with an internally threaded surface on the sleeve, wherein at least one of the threaded surface of the operating shaft and sleeve is plated. A ratchet wheel is received about the operating shaft, having oppositely disposed clutch surfaces positioned for engagement by the clutch collar portions of the operating shaft and the sleeve. A pinion is journaled on the operating shaft and is adjacent to the sleeve.
It is therefore a primary object of the present invention to provide a gradual release mechanism with a reduced release torque for a railway car hand brake.
It is a further object of the present invention to increase operator safety and minimize operating costs as a result by reducing the torque required to release the hand brake.
Still a further object of the present invention is to increase component life by reducing frictional forces between mating parts.
Still a further object of the present invention is to prevent premature failure of the hand brake as a result of worn components.